Special Issue "Two-Dimensional Electronics - Prospects and Challenges"

A special issue of Electronics (ISSN 2079-9292). This special issue belongs to the section "Microelectronics and Optoelectronics".

Deadline for manuscript submissions: closed (15 September 2015).

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Special Issue Editor

Guest Editor
Prof. Dr. Frank Schwierz

Institut für Mikro- und Nanotechnologien, Technische Universität Ilmenau, PF 100565, 98684 Ilmenau, Germany
Website | E-Mail
Interests: semiconductor device physics and simulation; novel transistor concepts; ultra-high-speed transistors; two-dimensional materials such as graphene, transistion metal dichalcogenides, and others, for electronic applications.

Special Issue Information

Dear Colleagues,

During the past 10 years, two-dimensional materials have found incredible attention in the scientific community. The first two-dimensional material studied in detail was graphene, and many groups explored its potential for electronic applications. Meanwhile, researchers have extended their work to two-dimensional materials beyond graphene. At present, several hundred of these materials are known and part of them is considered to be useful for electronic applications. Rapid progress has been made in research concerning two-dimensional electronics, and a variety of transistors of different two-dimensional materials, including graphene, transition metal dichalcogenides, e.g., MoS2 and WS2, and phosphorene, have been reported. Other areas where two-dimensional materials are considered promising are sensors, transparent electrodes, or displays, to name just a few. This Special Issue of Electronics is devoted to all aspects of two-dimensional materials for electronic applications, including material preparation and analysis, device fabrication and characterization, device physics, modeling and simulation, and circuits. The devices of interest include, but are not limited to transistors (both field-effect transistors and alternative transistor concepts), sensors, optoelectronics devices, MEMS and NEMS, and displays. Scientists and engineers active in the field are invited to submit either review papers or research papers on the exciting field of two-dimensional materials and their application in electronics.

Prof. Dr. Frank Schwierz
Guest Editor

Manuscript Submission Information

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Keywords

  • two-dimensional semiconductors
  • graphene
  • transition metal dichalcogenides
  • two-dimensional material preparation
  • nanoribbons
  • mobility
  • transistor
  • radio frequency
  • digital logic
  • device physics, modeling, and simulation

Published Papers (13 papers)

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Editorial

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Open AccessEditorial
Two-Dimensional Electronics — Prospects and Challenges
Electronics 2016, 5(2), 30; https://doi.org/10.3390/electronics5020030
Received: 2 June 2016 / Accepted: 2 June 2016 / Published: 7 June 2016
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Abstract
For about a decade, 2D (two-dimensional) materials have represented one of the hottest directions in solid-state research.[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle
Effect of Edge Roughness on Static Characteristics of Graphene Nanoribbon Field Effect Transistor
Electronics 2016, 5(1), 11; https://doi.org/10.3390/electronics5010011
Received: 13 September 2015 / Revised: 8 March 2016 / Accepted: 14 March 2016 / Published: 18 March 2016
Cited by 8 | PDF Full-text (3625 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a physics-based analytical model of GNR FET, which allows for the evaluation of GNR FET performance including the effects of line-edge roughness as its practical specific non-ideality. The line-edge roughness is modeled in edge-enhanced band-to-band-tunneling and localization regimes, [...] Read more.
In this paper, we present a physics-based analytical model of GNR FET, which allows for the evaluation of GNR FET performance including the effects of line-edge roughness as its practical specific non-ideality. The line-edge roughness is modeled in edge-enhanced band-to-band-tunneling and localization regimes, and then verified for various roughness amplitudes. Corresponding to these two regimes, the off-current is initially increased, then decreased; while, on the other hand, the on-current is continuously decreased by increasing the roughness amplitude. Full article
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Open AccessFeature PaperArticle
Simulation of 50-nm Gate Graphene Nanoribbon Transistors
Received: 2 November 2015 / Revised: 22 December 2015 / Accepted: 29 December 2015 / Published: 12 January 2016
Cited by 10 | PDF Full-text (2384 KB) | HTML Full-text | XML Full-text
Abstract
An approach to simulate the steady-state and small-signal behavior of GNR MOSFETs (graphene nanoribbon metal-semiconductor-oxide field-effect transistor) is presented. GNR material parameters and a method to account for the density of states of one-dimensional systems like GNRs are implemented in a commercial device [...] Read more.
An approach to simulate the steady-state and small-signal behavior of GNR MOSFETs (graphene nanoribbon metal-semiconductor-oxide field-effect transistor) is presented. GNR material parameters and a method to account for the density of states of one-dimensional systems like GNRs are implemented in a commercial device simulator. This modified tool is used to calculate the current-voltage characteristics as well the cutoff frequency fT and the maximum frequency of oscillation fmax of GNR MOSFETs. Exemplarily, we consider 50-nm gate GNR MOSFETs with N = 7 armchair GNR channels and examine two transistor configurations. The first configuration is a simplified MOSFET structure with a single GNR channel as usually studied by other groups. Furthermore, and for the first time in the literature, we study in detail a transistor structure with multiple parallel GNR channels and interribbon gates. It is shown that the calculated fT of GNR MOSFETs is significantly lower than that of GFETs (FET with gapless large-area graphene channel) with comparable gate length due to the mobility degradation in GNRs. On the other hand, GNR MOSFETs show much higher fmax compared to experimental GFETs due the semiconducting nature of the GNR channels and the resulting better saturation of the drain current. Finally, it is shown that the gate control in FETs with multiple parallel GNR channels is improved while the cutoff frequency is degraded compared to single-channel GNR MOSFETs due to parasitic capacitances of the interribbon gates. Full article
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Open AccessArticle
On the Stability and Electronic Structure of Transition-Metal Dichalcogenide Monolayer Alloys Mo1−xXxS2−ySey with X = W, Nb
Received: 2 November 2015 / Revised: 30 November 2015 / Accepted: 15 December 2015 / Published: 30 December 2015
Cited by 3 | PDF Full-text (3154 KB) | HTML Full-text | XML Full-text
Abstract
Layered transition-metal dichalcogenides have extraordinary electronic properties, which can be easily modified by various means. Here, we have investigated how the stability and electronic structure of MoS 2 monolayers is influenced by alloying, i.e., by substitution of the transition metal Mo by W [...] Read more.
Layered transition-metal dichalcogenides have extraordinary electronic properties, which can be easily modified by various means. Here, we have investigated how the stability and electronic structure of MoS 2 monolayers is influenced by alloying, i.e., by substitution of the transition metal Mo by W and Nb and of the chalcogen S by Se. While W and Se incorporate into the MoS 2 matrix homogeneously, forming solid solutions, the incorporation of Nb is energetically unstable and results in phase separation. However, all three alloying atoms change the electronic band structure significantly. For example, a very small concentration of Nb atoms introduces localized metallic states, while Mo 1 - x W x S 2 and MoS 2 - y Se y alloys exhibit spin-splitting of the valence band of strength that is in between that of the pure materials. Moreover, small, but evident spin-splitting is introduced in the conduction band due to the symmetry breaking. Therefore, transition-metal dichalcogenide alloys are interesting candidates for optoelectronic and spintronic applications. Full article
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Open AccessArticle
Equilibrium Molecular Dynamics (MD) Simulation Study of Thermal Conductivity of Graphene Nanoribbon: A Comparative Study on MD Potentials
Electronics 2015, 4(4), 1109-1124; https://doi.org/10.3390/electronics4041109
Received: 9 October 2015 / Revised: 22 November 2015 / Accepted: 15 December 2015 / Published: 21 December 2015
Cited by 28 | PDF Full-text (1913 KB) | HTML Full-text | XML Full-text
Abstract
The thermal conductivity of graphene nanoribbons (GNRs) has been investigated using equilibrium molecular dynamics (EMD) simulation based on Green-Kubo (GK) method to compare two interatomic potentials namely optimized Tersoff and 2nd generation Reactive Empirical Bond Order (REBO). Our comparative study includes the estimation [...] Read more.
The thermal conductivity of graphene nanoribbons (GNRs) has been investigated using equilibrium molecular dynamics (EMD) simulation based on Green-Kubo (GK) method to compare two interatomic potentials namely optimized Tersoff and 2nd generation Reactive Empirical Bond Order (REBO). Our comparative study includes the estimation of thermal conductivity as a function of temperature, length and width of GNR for both the potentials. The thermal conductivity of graphene nanoribbon decreases with the increase of temperature. Quantum correction has been introduced for thermal conductivity as a function of temperature to include quantum effect below Debye temperature. Our results show that for temperatures up to Debye temperature, thermal conductivity increases, attains its peak and then falls off monotonically. Thermal conductivity is found to decrease with the increasing length for optimized Tersoff potential. However, thermal conductivity has been reported to increase with length using 2nd generation REBO potential for the GNRs of same size. Thermal conductivity, for the specified range of width, demonstrates an increasing trend with the increase of width for both the concerned potentials. In comparison with 2nd generation REBO potential, optimized Tersoff potential demonstrates a better modeling of thermal conductivity as well as provides a more appropriate description of phonon thermal transport in graphene nanoribbon. Such comparative study would provide a good insight for the optimization of the thermal conductivity of graphene nanoribbons under diverse conditions. Full article
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Open AccessArticle
Dimensional Quantization and the Resonance Concept of the Low-Threshold Field Emission
Electronics 2015, 4(4), 1101-1108; https://doi.org/10.3390/electronics4041101
Received: 20 October 2015 / Accepted: 7 December 2015 / Published: 12 December 2015
Cited by 7 | PDF Full-text (205 KB) | HTML Full-text | XML Full-text
Abstract
We present a brief critical review of modern theoretical interpretations of the low-threshold field emission phenomenon for metallic electrodes covered with carbon structures, taking the latest experiments into consideration, and confirming the continuity of spectrum of resonance states localized on the interface of [...] Read more.
We present a brief critical review of modern theoretical interpretations of the low-threshold field emission phenomenon for metallic electrodes covered with carbon structures, taking the latest experiments into consideration, and confirming the continuity of spectrum of resonance states localized on the interface of the metallic body of the cathode and the carbon cover. Our proposal allowed us to interpret the double maxima of the emitted electron’s distribution on full energy. The theoretical interpretation is presented in a previous paper which describes the (1 + 1) model of a periodic 1D continuous interface. The overlapping of the double maxima may be interpreted taking into account a 2D superlattice periodic structure of the metal-vacuum interface, while the energy of emitted electrons lies on the overlapping spectral gaps of the interface 2D periodic lattice. Full article
Open AccessFeature PaperArticle
Electrical Compact Modeling of Graphene Base Transistors
Electronics 2015, 4(4), 969-978; https://doi.org/10.3390/electronics4040969
Received: 30 July 2015 / Revised: 22 October 2015 / Accepted: 2 November 2015 / Published: 18 November 2015
Cited by 4 | PDF Full-text (283 KB) | HTML Full-text | XML Full-text
Abstract
Following the recent development of the Graphene Base Transistor (GBT), a new electrical compact model for GBT devices is proposed. The transistor model includes the quantum capacitance model to obtain a self-consistent base potential. It also uses a versatile transfer current equation to [...] Read more.
Following the recent development of the Graphene Base Transistor (GBT), a new electrical compact model for GBT devices is proposed. The transistor model includes the quantum capacitance model to obtain a self-consistent base potential. It also uses a versatile transfer current equation to be compatible with the different possible GBT configurations and it account for high injection conditions thanks to a transit time based charge model. Finally, the developed large signal model has been implemented in Verilog-A code and can be used for simulation in a standard circuit design environment such as Cadence or ADS. This model has been verified using advanced numerical simulation. Full article
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Open AccessArticle
Enhanced Visibility of MoS2, MoSe2, WSe2 and Black-Phosphorus: Making Optical Identification of 2D Semiconductors Easier
Electronics 2015, 4(4), 847-856; https://doi.org/10.3390/electronics4040847
Received: 14 September 2015 / Revised: 13 October 2015 / Accepted: 21 October 2015 / Published: 28 October 2015
Cited by 21 | PDF Full-text (3529 KB) | HTML Full-text | XML Full-text
Abstract
We explore the use of Si3N4/Si substrates as a substitute of the standard SiO2/Si substrates employed nowadays to fabricate nanodevices based on 2D materials. We systematically study the visibility of several 2D semiconducting materials that are attracting [...] Read more.
We explore the use of Si3N4/Si substrates as a substitute of the standard SiO2/Si substrates employed nowadays to fabricate nanodevices based on 2D materials. We systematically study the visibility of several 2D semiconducting materials that are attracting a great deal of interest in nanoelectronics and optoelectronics: MoS2, MoSe2, WSe2 and black-phosphorus. We find that the use of Si3N4/Si substrates provides an increase of the optical contrast up to a 50%–100% and also the maximum contrast shifts towards wavelength values optimal for human eye detection, making optical identification of 2D semiconductors easier. Full article
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Open AccessArticle
Theoretical Analysis of Vibration Frequency of Graphene Sheets Used as Nanomechanical Mass Sensor
Electronics 2015, 4(4), 723-738; https://doi.org/10.3390/electronics4040723
Received: 8 April 2015 / Revised: 21 July 2015 / Accepted: 21 August 2015 / Published: 28 September 2015
Cited by 10 | PDF Full-text (418 KB) | HTML Full-text | XML Full-text
Abstract
Nanoelectromechanical resonator sensors based on graphene sheets (GS) show ultrahigh sensitivity to vibration. However, many factors such as the layer number and dimension of the GSs will affect the sensor characteristics. In this study, an analytical model is proposed to investigate the vibration [...] Read more.
Nanoelectromechanical resonator sensors based on graphene sheets (GS) show ultrahigh sensitivity to vibration. However, many factors such as the layer number and dimension of the GSs will affect the sensor characteristics. In this study, an analytical model is proposed to investigate the vibration behavior of double-layered graphene sheets (DLGSs) with attached nanoparticles. Based on nonlocal continuum mechanics, the influences of the layer number, dimensions of the GSs, and of the mass and position of nanoparticles attached to the GSs on the vibration response of GS resonators are discussed in detail. The results indicate that nanomasses can easily be detected by GS resonators, which can be used as a highly sensitive nanomechanical element in sensor systems. A logarithmically linear relationship exists between the frequency shift and the attached mass when the total mass attached to GS is less than about 1.0 zg. Accordingly, it is convenient to use a linear calibration for the calculation and determination of attached nanomasses. The simulation approach and the parametric investigation are useful tools for the design of graphene-based nanomass sensors and devices. Full article
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Review

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Open AccessFeature PaperReview
Graphene and Two-Dimensional Materials for Optoelectronic Applications
Electronics 2016, 5(1), 13; https://doi.org/10.3390/electronics5010013
Received: 21 January 2016 / Revised: 28 February 2016 / Accepted: 4 March 2016 / Published: 21 March 2016
Cited by 25 | PDF Full-text (2388 KB) | HTML Full-text | XML Full-text
Abstract
This article reviews optoelectronic devices based on graphene and related two-dimensional (2D) materials. The review includes basic considerations of process technology, including demonstrations of 2D heterostructure growth, and comments on the scalability and manufacturability of the growth methods. We then assess the potential [...] Read more.
This article reviews optoelectronic devices based on graphene and related two-dimensional (2D) materials. The review includes basic considerations of process technology, including demonstrations of 2D heterostructure growth, and comments on the scalability and manufacturability of the growth methods. We then assess the potential of graphene-based transparent conducting electrodes. A major part of the review describes photodetectors based on lateral graphene p-n junctions and Schottky diodes. Finally, the progress in vertical devices made from 2D/3D heterojunctions, as well as all-2D heterostructures is discussed. Full article
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Open AccessFeature PaperReview
Scalable Fabrication of 2D Semiconducting Crystals for Future Electronics
Electronics 2015, 4(4), 1033-1061; https://doi.org/10.3390/electronics4041033
Received: 8 October 2015 / Revised: 6 November 2015 / Accepted: 16 November 2015 / Published: 3 December 2015
Cited by 13 | PDF Full-text (8575 KB) | HTML Full-text | XML Full-text
Abstract
Two-dimensional (2D) layered materials are anticipated to be promising for future electronics. However, their electronic applications are severely restricted by the availability of such materials with high quality and at a large scale. In this review, we introduce systematically versatile scalable synthesis techniques [...] Read more.
Two-dimensional (2D) layered materials are anticipated to be promising for future electronics. However, their electronic applications are severely restricted by the availability of such materials with high quality and at a large scale. In this review, we introduce systematically versatile scalable synthesis techniques in the literature for high-crystallinity large-area 2D semiconducting materials, especially transition metal dichalcogenides, and 2D material-based advanced structures, such as 2D alloys, 2D heterostructures and 2D material devices engineered at the wafer scale. Systematic comparison among different techniques is conducted with respect to device performance. The present status and the perspective for future electronics are discussed. Full article
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Open AccessFeature PaperReview
Towards the Realization of Graphene Based Flexible Radio Frequency Receiver
Electronics 2015, 4(4), 933-946; https://doi.org/10.3390/electronics4040933
Received: 27 September 2015 / Revised: 30 October 2015 / Accepted: 2 November 2015 / Published: 11 November 2015
Cited by 6 | PDF Full-text (1452 KB) | HTML Full-text | XML Full-text
Abstract
We report on our progress and development of high speed flexible graphene field effect transistors (GFETs) with high electron and hole mobilities (~3000 cm2/V·s), and intrinsic transit frequency in the microwave GHz regime. We also describe the design and fabrication of [...] Read more.
We report on our progress and development of high speed flexible graphene field effect transistors (GFETs) with high electron and hole mobilities (~3000 cm2/V·s), and intrinsic transit frequency in the microwave GHz regime. We also describe the design and fabrication of flexible graphene based radio frequency system. This RF communication system consists of graphite patch antenna at 2.4 GHz, graphene based frequency translation block (frequency doubler and AM demodulator) and graphene speaker. The communication blocks are utilized to demonstrate graphene based amplitude modulated (AM) radio receiver operating at 2.4 GHz. Full article
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Open AccessReview
Two-Dimensional Materials for Sensing: Graphene and Beyond
Electronics 2015, 4(3), 651-687; https://doi.org/10.3390/electronics4030651
Received: 3 August 2015 / Revised: 8 September 2015 / Accepted: 14 September 2015 / Published: 18 September 2015
Cited by 106 | PDF Full-text (2382 KB) | HTML Full-text | XML Full-text
Abstract
Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, [...] Read more.
Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications. Full article
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